Read this quite old reply by forever-d to a post about hostile action against the bitcoin network, though it just had to be posted afresh.
Personally I don't agree with the concept of pirating stuff that others worked to produce, but the sentiment and logic here are elegant to say the least!
Since you are using p2p filesharing networks as an analogy...
Government crackdowns actually stengthened the p2p filesharing ecosystem instead of weakening it.
Government crackdowns acted like something of an evolutionary pressure; for every filesharing network that was successfully destroyed, a new generation of better, stronger ones sprang up.
Napster relied on a single centralised server. The government shut down the server. Result? Several Napster clones that could support multiple servers. Then the government started taking down servers one by one. Result? Serverless technology. Then the government started prosecution of individual users. Result? Proliferation of VPN providers and pseudonymous p2p. And so on....
I doubt we would have a lot of innovative technologies today (eg. i2p, tor, bittorrent) if governments simply had left Napster alone. Talking about unintended consequences!
Government may succeed in destroying the current block chain. It may even succeed in destroying the current implementation of the Bitcoin protocol. But it will never destroy the source code, the meme, the spirit, and the community. The p2p cryptocurrency genie is out of the bottle.